A 45-year-old woman is evaluated in the emergency department for severe, progressive abdom… — USMLE Step 3

A 45-year-old woman is evaluated in the emergency department for severe, progressive abdominal distension and right upper quadrant pain that began 4 days ago. She also reports intense, generalized itching that typically occurs after taking warm showers. Her past medical history is significant for peptic ulcer disease. She takes no medications. Her temperature is $37.2^\circ C$ ( $99.0^\circ F$ ), blood pressure is $145/88$ mmHg, heart rate is 98/min, and respiratory rate is 18/min. Physical examination reveals a ruddy facial complexion. The jugular venous pressure is $6$ cm $H_2O$ . Abdominal examination shows marked distension, shifting dullness, and a palpable, tender liver edge $5$ cm below the right costal margin. There is no lower extremity edema.

Laboratory studies show:
Hemoglobin: $18.8$ g/dL
Hematocrit: 56%
Leukocytes: $12,500 / \mu L$
Platelets: $620,000 / \mu L$
Serum total protein: $6.8$ g/dL
Serum albumin: $3.5$ g/dL
Total bilirubin: $2.1$ mg/dL
Direct bilirubin: $0.8$ mg/dL
Aspartate aminotransferase (AST): 185 U/L
Alanine aminotransferase (ALT): 210 U/L

Diagnostic paracentesis yields 1.5 L of straw-colored fluid. Ascitic fluid analysis reveals:
Albumin: $1.4$ g/dL
Total protein: $2.9$ g/dL
Neutrophils: $80 / \mu L$

Based on the laboratory and clinical findings, which of the following is the most likely underlying mechanism for this patient's abdominal fluid accumulation?

A
Right-sided myocardial dysfunction
B
Cirrhotic portal hypertension
Hepatic venous outflow obstructionAnswer
D
Peritoneal malignant infiltration
E
Glomerular basement membrane disruption

Answer

The correct answer is hepatic venous outflow obstruction.

The correct answer is hepatic venous outflow obstruction. This patient's clinical presentation of aquagenic pruritus, ruddy complexion, and elevated hemoglobin, leukocytes, and platelets is highly indicative of polycythemia vera. Myeloproliferative disorders are major risk factors for atypical venous thromboses, including Budd-Chiari syndrome (hepatic vein thrombosis). To determine the etiology of ascites, the serum-ascites albumin gradient (SAAG) is calculated. This patient's SAAG is

3.5 - 1.4 = 2.1

g/dL. A SAAG

\geq 1.1

g/dL demonstrates that portal hypertension is the driving force behind the fluid accumulation. Next, the ascitic fluid total protein must be evaluated to differentiate the cause of portal hypertension. An ascitic total protein

\geq 2.5

g/dL indicates that the hepatic sinusoids are intact and allowing protein to leak, which points specifically to post-sinusoidal portal hypertension. Causes of post-sinusoidal portal hypertension include right ventricular failure, constrictive pericarditis, and Budd-Chiari syndrome. Because the patient's jugular venous pressure is normal (

6

H_2O

) and there is no peripheral edema, cardiac etiologies are excluded, leaving hepatic venous outflow obstruction as the diagnosis.

Step-by-Step Solution

Calculate the serum-ascites albumin gradient (SAAG) by subtracting the ascitic fluid albumin from the serum albumin.

\text{SAAG} = 3.5 - 1.4 = 2.1 \text{ g/dL}

A SAAG

\geq 1.1

g/dL confirms the presence of portal hypertension as the primary driver of the ascites.

Evaluate the ascitic fluid total protein.

Ascitic total protein is

2.9

g/dL (which is

\geq 2.5

g/dL).

In the setting of portal hypertension, a high ascitic total protein (

\geq 2.5

g/dL) indicates intact hepatic sinusoids, localizing the pathology to a post-sinusoidal etiology (e.g., Budd-Chiari syndrome or right-sided heart failure).

Synthesize the laboratory interpretation with the clinical presentation.

The patient has signs of polycythemia vera (pruritus, panmyelosis) creating a hypercoagulable state, alongside a normal jugular venous pressure (

6

H_2O

The normal jugular venous pressure rules out right-sided heart failure, making hepatic venous outflow obstruction (Budd-Chiari syndrome) the most likely diagnosis.

Key Concept

Ascitic fluid analysis using SAAG and total protein accurately localizes the etiology of ascites; a SAAG >= 1.1 g/dL with total protein >= 2.5 g/dL indicates post-sinusoidal portal hypertension.

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic